Switching mechanism



May 30, 1944. e. E. ATKINS SWITCHING MECHANISM Filed Oct. 1. 1942 wvmroe. By. 6 .EA TK/NS ATTORNEY Patented May 30, 1944 SWITCHING MECHANISM George E. Atkins, Glen Ridge, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 1, 1942, Serial No. 460,369

4 Claims.

This invention relates to improvements in .switching mechanisms and particularly to automatic switches employed 'in the telephone art.

An object is to simplify and reduce the cost of manufacturing restoring spring assemblies as employed in such switches and to facilitate the assembling and adjusting of said assemblies.

The invention is particularly applicable to automtaic switches in which wipers mounted on a central shaft are caused to establish connections with terminals in the banks by the lifting and rotating of the shaft. To return the shaft and Wipers to normal from the rotated position. t has been the practice to employ a restoring spring assembly including a bushing surrounding a sleeve extension on the shaft. This bushing is connected at the top to a cap and a helical spring surrounding the bushing. The bushing is secured to the sleeve extension by means of a straight pin extension from the spring which protrudes diagonally across the bushing through slot-s therein and in the sleeve. In this case the bushing serves to maintain the spring'more or less in concentric relation with the shaft, and the cap serves as an engagement surface for the winding of the spring to the proper tension.

The present invention relates to a simplified restoring spring assembly of this general character for returning the shaft in switches of this kind to normal position, and a feature thereof is an arrangement including merely a single cap which may be drawn from a tubing to form an upper cylindrical top portion and a lower squareshaped bottom portion connected by an intermediate cone-shaped portion which is somewhat flattened out on two opposite sides. The straight pin extension on the spring is threaded through holes in the cone-shaped section and engages the slot in the sleeve extension of the shaft. The upper or last turn of the spring in accordance with the applicants invention is wrapped tightly around the cone-shaped section of the cap so that when the spring is wound, this turn will be pressed up against the cone-shaped section and thereby force the succeeding turns of the spring to maintain themselves concentric with each other on the sleeve. The upper cylindrical portion of the cap serves as an engagement surface for w nding the spring. Advantages of substituting the present invention in place of the cap and bushing ii" the prior art return spring assemblies are to reduce the cost of manufacture and cost of material and to simplify the assembling and adjusting of the mechanism and at the same time ma ntain the spring turns concentric with each other net may also be on the sleeve without the aid of the prior art cap and bushing assembly which, as stated, consists of two machined parts which must be assembled together with the spring and which conta n considerably more material.

The invention has been illustrated in the accompanying drawing, in which:

Fig. 1 shows an automatic switch to which the applicants invention has been applied;

Fig. 2 shows a perspective of the cap portion of the applicants invention;

Fig. 3 shows this cap with a part of the spring and sleeve extension attachment looking from the bottom of the cap;

Fig. 4 shows the cap, a portion of the upper end of the spring, the sleeve extension and the lower end of the spring connected to a stationary member;

Fig. 5 is a cross section taken on line 5-5 of Fig. 3; and

Fig. 6 shows partially in section the connecting means between the main shaft and the sleeve extension thereof.

Referring now to the drawing, Fig. 1 illustrates a typical step-by-step switching structure em ployed in automatic telephone systems to establish connections between lines and consists essentially of a frame I, a vertical stepping magnet 2 having an armature and a pawl 3 for lifting the shaft 4 by engaging the toothed rack 5 on the shaft. A rotary magnet l is provided having an armature 8 and a pawl (not shown) attached thereto for rotating the shaft 4 by engaging the ratchet wheel ID on the shaft 4. A release magprovided which is not visible it is hidden. by its armature II. This armature operates on pawls such as l2 for releasing the shaft to return to a normal position, first by rotating back to normal and then by dropping down by gravity from its lifted position. To the shaft 4 are connected wipers, one group of which has been shown at l3 that may engage terminals in a switch bank (not shown), The restoring spring assembly in accordance with the applicants invention has been applied to this shaft 4 for restoring it to normal in the rotary direction. As shown in Figs. 1 and 6 in particular, the shaft terminates at the top inside the extension sleeve M. to which it is secured by means of a rotary stop member I5 that engages a key slot in the sleeve and a similar key slot in the shaft. This stop member I 5 is held in place by a screw it which is inserted in a bracket or clamp l1 surrounding said sleeve. Resting on top of the clamp I I is a bracket I8 secured to a collar I9 the shaft has been lifted and rotated, the spring.

25 is tensioned by having its upper end connected to the cap 28 and the sleeve l4 and the lower end anchored in the bracket I8-which is maintainedstationary as far as any rotary movement is concerned but travels with the shaft upwardly while engaging the stationary post M. This tension in spring 25 will, therefore, cause the shaft to rotate back to normal when released by the release pawl l2. v

Referring now specifically to Figs. 2 to the specific construction and function of the cap 28 will be described. This cap consists of an upper cylindrical top portion 30, a square-shaped bottom portion 3! and an intermediate cone-shaped portion 32 connecting the portions36 and 3i. It will be noted that this cone-shaped portion 32 is slightly flattened out 'at two opposite sides, of the square portion 3!, as shown at 33 and 34. To assemble this cap with the spring and sleeve 14, the spring is provided with a straight pin extension 35 extending diagonally across the last turn 36 of the spring which is threaded through holes 3! and 38 in the sides 33 and 33 of the square-shaped portion 3| and caused to engage slots such as the slot 40 in the sleeve [3. The sides 33 and 34 permit the extension 35 to be bent from the spring at an easy curve from the last turn 36 as shown at 39 and this extension may also protrude a certain distance from the hole 38 without interference and to prevent the spring from becoming disconnected from the cap. The cap 23 and spring 25 are thereby secured to the sleeve l4 for rotation therewith. The lower end of the spring 25 is as stated anchored to an extension 26 of the bracket I8 and surrounds at its lower end the collar 19. It should now be observed that the upper or first complete turn 36 of the spring 35 engages closely the cone-shaped portion 32 as shown particularly in Figs. 3 and 5..

In Fig. 5 this turn 36 is shown engaging at M and 42 this cone-shaped portion 32. It has been discovered that all the coils in the spring 25 are. by this means always maintained concentric with each other on the sleeve {4 while the spring is tensioned, as the pressing upward ofthe turn 36 on the cone-shaped portion 32 gives to the succeeding turns of the spring 25 a certain. torque or tension which enables them to maintain themselves in this concentric relation to each other on the sleeve 14 during the tightening as well as during the unwinding of the spring. This cap 28 may be manufactured by drawing or stamping. the metal from which it is made into the desired shape. This is a simple operation. The upper part of the upper cylindrical portion is employedv as heretofore as engagement surfaces in tightening the spring originally to give it the desired tension for returning the shaft to normal. The inside dimension of the square-shaped portion 3! is but slightly larger than the outside diameter of the sleeve M, so that the cap and the spring will be maintained practically concentric with the sleeve. v

" shaped portion of the collar, said spring being wrapping of a last turn of the spring around the cone-shaped portion and by having the end of the spring straight and running diametrically across the sleeve through the opposite slots therein and corresponding apertures in the conethereby, when Wound, tensioned against the coneshaped portion of the collar to position its succee'ding turns concentrically with each other on the sleeve.

2. In combination, a shaft, a sleeve connected to said shaft having diametrically opposite slots at the free end thereof, a bracket associated with said sleeve, a helical spring surrounding said sleeve having one end secured to said bracket, a collar having an enlarged circular end, a smaller square end and an intermediate connecting portion with two opposite sides cone-shaped and the other two opposite sides flat and slanting, the opposite end of said spring being wrapped around said connecting portion and ending in a straight end, threaded diametrically across the opening the diametrically opposite slots in said sleeve to lock said end of the spring and the collar to the sleeve, the opening in the square portion of the collar being slightly larger than the outside diameterof the sleeve to prevent the collar from binding on the sleeve, the cone-shaped connecting portion of the collar being at its base larger in diameter than the inside diameter of the spring so that when the spring is wound it will be tensioned against this cone-shaped portion to position its turns concentrically with each other and with the collar, the large circular end of the collar serving as a hand-engagement surface for winding the springs. i

3. In combination, a shaft, a sleeve connected to said shaft, having diametrically opposite slots at the free end thereof, a bracket associated with said. sleeve, a helical spring surrounding said sleeve having one end secured to said bracket, a

collar drawn into a large cylindrical top portion,

a smaller square bottom portion and an intermediate connecting portion having two conioallyshaped opposite portions extending from the top portion and merging into two opposite surfaces of the square portion and two flat slanting opposite portions connecting the other two opposite surfaces of the square portion with the top portion, the opposite end of the spring having one turn wrapped around the cone-shaped portions and extending in a straight end diametrically across the sleeve through the opposite'slots there} in and through opposite apertures in the'fiat portions and locked in the slots in said sleeve to secure the spring to the collar and to the sleeve, said one turn of the spring serving when the spring is wound to tighten itself around the coneshaped portions and thereby tensionthe succeeding turns of the spring so that they will be held concentric to each other on the sleeve.

4. In combination, a shaft, a sleeve connected at one end to said shalt, having diametrically opposite slots at the opposite free ends thereof, a bracket mounted on said sleeve, means for holding said bracket from rotating on said sleeve and for causing it to move with said sleeve in a longiudlnal direction, a helical spring loosely surrounding said sleeve and having one end secured to said bracket, a collar drawn into an upper large cylindrical top portion, a smaller square bottom portion and an intermediate connecting portion, said connecting portion having two diagonally opposite cone-shaped sides extending with their wide ends from the top portion and merging into corresponding opposite sides of the square portion and having two diagonally opposite flat sides slanting from the top portion to merge with the corresponding diagonally opposite other sides of the square portion, the opposite end of said spring having the last turn wrapped around the cone-shaped sides and extending from this last turn by an easy curve into a straight end which lies diagonally across said last turn and is threaded through the opposite slots in the sleeve, and through diagonally located opposing apertures in the flat sides of the intermediate connecting portion of the collar to lock said spring in the slots in said sleeve and to secure the spring to the collar and to the sleeve, said last turn of the spring serving when the spring is wound to tighten itself around the cone-shaped sides of the collar and thereby cause the remaining turns of the spring to align themselves concentrically to each other around said sleeve.

GEORGE E. ATKINS. 

